In the field of visual arts such as the theater industry there are many requirements for compact portable light sources that are adjustable so they can be set up flexibly for the requirements of particular scenarios. Traditionally such adjustable light source have often utilized incandescent lighting as evidenced by the stereotype of actors and musicians sweating under the heat of powerful incandescent lamps. The inherent characteristic of the incandescent lamp in approximating a point source of light lends itself to optical processing especially for narrow beam spotlights, however an elongated tubular shape is more suited to “washing” designated areas uniformly and can be implemented with fluorescent lamps which offer the further advantage of being much more electric power efficient. Typically two or four tubular fluorescent lamps can produce results that would require an array made from a large quantity of individual incandescent lamps.
A key parameter in portable “wash” lighting units is the angle of beam spread between the half power illumination limits relative to the longitudinal central axis, since this determines the concentration and the coverage of a single unit and determines the spacing and quantity required when a plurality of such units are deployed for uniform illumination over a large area.
In compact fluorescent units of known art, the beam spread is a fixed parameter that is set in design by the shape of the reflector and the relative location of the fluorescent lamps. Thus, to accommodate a required range of beam spreads, a supplier or user must stock numerous versions of the unit in different models, each with a different beam spread rating, typically ranging from 60 to 90 degrees, or use additional accessories that attach to the front of the fixture to alter the beam.